Description (taken directly from the application): The objectives and Specific Aims are to provide mouse, rat, and porcine islet tissue to the participants of the PPG for their in vitro studies on immune rejection mechanisms and islet function, for gene transfer experiments, and for transplantation. In addition, the techniques of islet cell transplantation will be taught to investigators and their lab members as required. Background: This PPG is focused upon islet transplantation, with the expectation that porcine islets will be transplanted into humans with IDDM. Because of the serious shortage of human islet tissue, it will probably be necessary to use islets from other species. For a variety of reasons, including ready availability, pigs seem particularly well suited for xenografting. Therefore, both adult porcine islets and porcine neonatal pancreatic cell clusters (NPCCs) will be made available to the participants of the PPG. NPCCs seem particularly promising because they are hardy, have impressive capacity for growth and differentiation, and seem particularly well suited for genetic modification. Rat and mouse islets will also be supplied to the four Projects. Although the goal of this work is to transplant genetically modified pig islets into primates, a large amount of background work must first be carried out with rodent islets, which have proved to be the most widely used models for the study of islet transplantation immunology, as well as islet physiology and cell biology.